A metal layer of Group 5 metal, particularly tantalum (Ta) and niobium (Nb), and an oxide layer or nitride layer of tantalum and niobium can be used for manufacturing semiconductor devices. Particularly, a method of forming a tantalum-containing layer by sputtering has been used in manufacturing process of semiconductor devices. However, in order to form an extremely thin (several nm thick) tantalum-containing layer such as a copper diffusion barrier on an uneven surface, a chemical deposition method with excellent step coverage, particularly an atomic layer deposition method, is needed, and, thus, a Group 5 metal precursor compound suitable therefor is needed.
Pentakis(dimethylamido)tantalum (PDMAT), (tert-butylimido)tris(diethylamido)tantalum (TBTDET), (tert-butylimido)tris(diethylamido)niobium (TBTDEN), etc. have been known as organic metal precursor compounds capable of forming Group 5 metal-containing layers (see U.S. Pat. No. 6,552,209) However, PDMAT is solid and thus inconvenient for use in the chemical deposition method or the atomic layer deposition method. A liquid source is advantageous for use in the chemical deposition method or the atomic layer deposition method. A direct liquid injection (DLI) system configured to vaporize a liquid in a cylindrical container or vaporize a liquid injected at a constant flow rate has been widely used in manufacturing process of semiconductor devices. However, the rate of sublimation of a solid is proportional to the surface area of the solid which continues to change during sublimation, and, thus, it is difficult to regularly vaporize and supply the solid and a special device is needed. Further, all of PDMAT, TBTDET, and TBTDEN are poor in thermal stability and thus disadvantageous for use at high temperature. For example, it is difficult to use the compounds in the atomic layer deposition method for forming a uniform-thickness oxide layer on an uneven surface at 300° C. Accordingly, there is a need for a novel Group 5 metal precursor compound which can be used in commercial manufacturing process of semiconductor devices and has high thermal stability and is in a liquid state or viscous solid state at room temperature.